Low-Carb Olive Oil Cake

Heat the oven to 325u0b0 F. Grease a 9-inch cake pan that is at least 2 inches deep or cast-iron skillet and line the bottom with parchment paper.
In a large bowl, whisk the almond and coconut flours, sweetener, salt, baking soda, and cream of tartar.
In another large bowl, whip the egg whites with a hand mixer, starting on low speed and gently building to high, until soft peaks form. Set aside.
In a third large bowl, whisk the olive oil and egg yolks together to emulsify. Then add in the milk, orange zest and orange juice.
Add the olive oil/milk/orange mixture to the dry ingredients and whisk to combine.
Lighten the mixture with a dollop of whipped egg white, then add the rest in and stir gently until all egg mixture is thoroughly incorporated (no streaks of white) but not overmixing so as not to deflate the egg whites.
Pour the batter into the prepared pan and cover with foil. Bake for 45 minutes.
Remove the foil and bake for an additional 45 minutes or until set in the center and a tester comes out clean. Check for doneness after about 20 minutes but keep it in as long as you can--this cake is very moist and needs plenty of time in the oven but it's a balancing act between doneness and overbrowning.
Transfer the cake to a rack and let cool for 30 minutes.
Run a knife around the edge of the pan, invert the cake onto the rack and let cool completely, 2 hours. As with most gluten-free baked goods, this is best sliced and eaten when completely cooled to avoid crumbling.